Access network for mobile telecommunications and method for developing radio coverage

ABSTRACT

A telecommunications network for mobile phone users comprising a user subsystem and a transport subsystem associated by means of an access subsystem, which connect to them respectively through a user access communication interface and a transport access communication interface suitable to allow the exchange of data flows between said subsystems, the access subsystem identifying a coverage area of the telecommunication network for mobile users characterized in that said access subsystem determines on the territory a separated cellular coverage for the transmission from the user subsystem to the network with respect to that from the network to the user subsystem, said access subsystem STA) being composed from, in addition to bidirectional base stations, as known, also from stations suitable to support monodirectional transmission in uplink or in downlink.

BACKGROUND OF INVENTIONS

The present invention relates to a telecommunications network for mobileusers, said telecommunications network for mobile users comprising auser's subsystem and a transport subsystem connected by means of anaccess subsystem, which offers them respectively a user accesscommunications interface and a transport access communicationsinterface, suitable to permit the exchange of the information flowsamong said subsystems, said access subsystem identifying a coverage areaof the cellular telephone network, through the composition of elementarycoverage areas called cells, each one generated by a radio base stationthat ensures the birectional communication among user subsystems andaccess subsystem.

Based on various analyses, it is expected that in a short time we willsee a large increase in the quantity of information exchanged betweenusers equipped with mobile radiotelephone terminals and the networks ofthe providers of such services.

In light of such future needs, various national and internationalorganizations (e.g. ITU, ETSI, FCC, etc.) dealing with regulationsaffecting radio frequencies allocation and utilization and the relativestandards of data processing and signal modulation techniques, agreed onthe definition of standards (or a group of standards like the IMT 2000)which allows a significant increase in the velocity of exchange of databetween the mobile networks and the user mobile terminal and vice versa.The IMT 2000 group of standards, for example, includes the new standardscalled CDMA 2000 and Universal Mobile Telecommunications System (UMTS)or 3G (third generation) that allow video-conferencing and compatibilitywith the protocols of Internet networks (e.g., Ipv6) with other networksof the same family (e.g., DECT), and with the previous generation (2G)wireless telephone networks (e.g., GSM and PCS) and their improved datatransport versions such as GPRS, EDGE, etc., (usually referred to as2.5G).

At the same time, methodologies and standards are continuously developedand perfected for the treatment of signals able to minimize thebandwidth requirements for digital transmissions of audio and videosignals permitting the efficient transport of music, voice and images ondigital networks such as Internet, Intranet and the like.

There is, therefore, reason to believe that the diffusion of newterminals capable of efficient connection to the Internet, to watchvideos and to reproduce data, voice, music and television filesdownloadable from the Internet will bring significant growth in thequantity of data carried by the terrestrial radio networks for the nextgeneration of mobile phones. For example, the third generation cellularsystems, using the UMTS standard, are designed for multimediacommunications. These person-to-person communications can be improvedwith quality images and/or video and access to information or serviceson the private or public networks can benefit from the high availabledata rate and from the increased communication flexibility of suchsystems.

These systems offer the following characteristics:

-   -   variable bit rate to furnish bandwidth compatible with the        service needed (from 16 kbps for voice to 2 Mbps for “High        Multimedia”);    -   multiplexing services with different quality requirements in a        single connection;    -   delay requirements for real time traffic;    -   quality requirements from 10% frame error to 10⁻⁶ bit error        rate;    -   compatibility with 2G systems (e.g., GSM) and handover        intersystems for better coverage and traffic balance;    -   high efficiency in spectrum utilization    -   compatibility of Frequency Division Duplex (FDD) and Time        Division Duplex (TDD) connection modes    -   support of asymmetric traffic for uplinks (from user to        provider) and downlinks (from provider to user).

Among the most important characteristics of the network based on theUMTS standard are the increased bit rate for the user, compatibilitywith Internet standards, the ability to run multimedia files and theability of connecting to the terminal in an “always on” mode.

It is also logical to envision that in the beginning the use of the UMTSnetwork will be primarily made of voice and Internet traffic and thatthe rate of multimedia traffic will increase over time.

Since the requested information will frequently be available through theInternet, it is important to provide efficient management of TCP/UDP/IPtraffic on the UMTS network. In order to be successful, the UMTS networkmust be able to support a wide array of applications from differentrequirements for performance and quality of service.

Further, there are technologies in rapid and constant development, whichcompete in the production of portable radio terminal (user terminals),which are able to incorporate functions beyond basic telephonesservices, such as the various additional complex functions. Theseinclude graphic visualization with good resolution, typical functions ofPersonal Computers, capability to interpret and process variousstandards and protocols of the Internet, storage of large quantities ofdata, elaboration and reproduction of audio and video files based onvarious standards, ability to run serial interfaces via cable toinfrared and radio for data exchange over short distances with otherdigital units, reception and elaboration of GPS signals, execution ofcomplex interactive games, quick execution of cryptographic codes andvoice recognition and synthesis, etc.

All of these capabilities of the user terminal necessary to support thevast array of services foreseen by the 3G mobile telecommunicationsnetworks will result in a notable increase in energy consumption. Thisincrease in energy consumption over and above today's 2G terminals(primarily for telephones) will make even more important methodologiesaimed at optimizing energy consumption.

Thus, to furnish a service qualitatively acceptable to customers, thewireless network providers will be forced to continuously upgrade theircapacity to meet increased demand. If the demand for new mobile networkservices continues, problems can surface with regard to capacity both onthe transport networks and the access networks. To augment the transportcapacity, it will be necessary to increase the capacity of variousconnections, which are theoretically limited only by cost. The accesscapacity is limited instead by the finite frequency band assigned toeach provider. Reducing the dimensions of the coverage cells and thusincreasing their numbers can manage the increases in capacity, but thissolution presents technical problems if pushed to the extreme and is anendeavor that has its limits.

The UMTS network consists of, at the network architecture level, anassembly of network elements, each with a specific function. At thelevel of standards, both the logical elements and the open interfacesare defined in a way that makes automatically possible to pick out thephysical elements of the network as well.

The presence of open interfaces, in particular in the UMTS TerrestrialRadio Access Network (UTRAN), allows interconnections to the UMTSnetwork in ways not explicitly foreseen by the current standards.

Documentation of the detailed description of services and standardizedperformance (or those currently being defined) for the 2.5G and 3Gmobile telecommunications networks has been produced by the ThirdGeneration Partnership Project (3GPP) and the Third GenerationPartnership Project 2 (3GPP2). A synthesis of this information isavailable in publications such as, “WCDMA for UMTS” by Holma andToskala, 2000, John Wiley & Sons, while FIG. 1, described below, showssome of the UMTS network elements necessary to describe the invention.

FIG. 1 represents a block diagram at the highest architectural level ofa telecommunications network for mobile phone users UNET of the typenoted in the UMTS standard. It comprises three subsystems allinterconnected as follows:

-   -   user terminal subsystem STU that is indicated in the standard as        “User Equipment”. This subsystem makes up the user terminal        system, i.e. the portable terminal, such as for example, a        cellular phone. This user terminal subsystem is interconnected        to the telecommunications network for mobile phone users UNET,        in particular to an access subsystem STA, by means of a user        access interface Uu through which a data and voice signal TS is        received and transmitted. This user access Uu interface, which        has been referred to as an open interface so as to allow it to        function in association with high quality terminals. The user        terminal subsystem is made of a user identification module USIM,        similar to the SIM card of the GSM standard, and the mobile        equipment ME, i.e. the cellular phone, that communicates through        appropriate interface equipment Cu;    -   access subsystem STA: this subsystem constitutes of the access        network for the UMTS standard, the previously mentioned system        UTRAN and connects to the transport network STT by means of a        transport access Iu interface;    -   transport subsystem STT: said transport subsystem STT identified        as “Core Network” in the UMTS standard constitutes the transport        network of the UMTS system. Said subsystem STT, in addition to        being connected by means of a transport access Iu interface to        the access subsystem STA, must be able to interconnect with all        the other existing networks (external networks, PSTN, ISDN,        B-ISDN, Internet, etc.), which are identified in FIG. 1 by a        block EXTNET. In this transport subsystem STT are comprised the        information switching capabilities that are typical of cellular        telephone systems. Namely, a Mobile Service Switching Center        (MSC), a Home Location Register (HLR) database, a Visitor        Location Center (VLR) database, an interconnection node or        gateway GMSC, a node for the management of the packet switching        SGSN Serving GPRS Support Node, and an interconnection node, or        gateway, of the apparatus for packet switching GGSN (Gateway        GPRS Support Node).

In FIG. 1 it is shown, inside of the access subsystem STA, the basestations SNB that correspond to the base stations shown as Node-B in theUMTS standard. Namely, the radio stations disseminated through theterritory of the mobile telephone system. Their principal functionconsists of exchanging, by means of the radio interface Uu, the data andvoice signal TS with the user terminal subsystem STU. These basestations SNB also run the principal radio resources like, for example,the internal power control. Inside the access subsystem STA is compriseda radio network controller CRR as it is defined on the UMTS standard.This radio network controller CRR has complete control of all the radioresources in its domain. Namely, the base stations SNB connected to itby means of an appropriate controller station interface Iub.

The radio network controller CRR controls the working of one or morebase stations SNB, controls the setting of radio channels (establishmentand release connections), frequency hopping, internal handovers andother functions, communicating with the transport subsystem STT, inparticular, with the switching center MSC. In large urban areas, thereare a large number of base stations SNB controlled by a small number ofradio network controllers CRR.

Each base station SNB is able to manage through the user/accessinterface Uu the connection to the network UNET of all the usersubsystems STU that are located in the area surrounding the base stationSNB; such an area, managed by one only base station SNB, is called cell.Base stations SNB are placed over the territory in a way to covercontinuously the territory itself, minimizing the areas in which radiocoverage is not sufficient. The aim is to allow the moving usersubsystem STU to be connected continuously to the UNET network.

The user subsystem STU that are inside a certain cell exchange databidirectionally with the base station SNB that identifies that cell:thus communication from user subsystem STU to base station SNB (Uplinktransmission) and from base station SNB to user subsystem STU (downlinktransmission) is obtained.

Due to the predictable rise in requests for multimedia information, theUNET network described in FIG. 1, must carry growing traffic from theexternal networks EXTNET to the transport/access interface Iu andaccess/user Uu in two directions.

As mentioned, to furnish a service qualitatively acceptable to thecustomers, the providers of UMTS type networks and wireless in general,will be forced to continue their investment in balancing networkcapacity with the increasing growth in demand.

In order to solve the above cited problem of increasing download datarequirements, a telecommunication network has been disclosed by documentEP 1 122 962 A, where several additional radio base stations provideadditional monodirectional downlink channels. This solution has theproblem of increasing electromagnetic pollution due to the irradiatedelectromagnetic power, and it does not solve the problem of theincreasing consumption of the third generation terminals.

SUMMARY OF THE INVENTION

The present invention has for aim to solve the cited problems and toindicate an improved and more efficient telecommunication network formobile phone users.

Under this frame, the main object of the present invention is toindicate a telecommunications network for mobile phone users that isable to serve a greater number of users with the same number oftransmitting stations.

A further object of the present invention is to indicate atelecommunications network for mobile phone users that allows forreducing the energy consumption in transmission on the terminal side.

A further object of the present invention is to indicate atelecommunications network for mobile phone users that is compatiblewith the new cellular phone standards, in particular the UMTS standard.

In order to achieve such aims, it is the object of the present inventionto provide a telecommunications network for mobile users and/or basestation and/or radio network controller and/or a method/means forsending information incorporating the features of the annexed claims,which form an integral part of the description herein.

DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of the present invention willbecome apparent from the following detailed description and annexeddrawings, which are supplied by way of non limiting example, wherein:

FIG. 1 shows a basic diagram of a mobile telecommunications networkaccording to the prior art;

FIG. 2 shows a basic diagram of the access subsystem STA of atelecommunications network for mobile users UNET according to theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention is based on the observation that a large amount of newmultimedia traffic will manage bidirectional connections developed usingFrequency Division Duplex (FDD) technology. Toward this end, it has beenconceived a network architecture that, keeping in mind the new standard,allows to significantly increase the capacity in the most cost effectivemanner possible.

It seems desirable, therefore, to develop future UMTS terrestrialnetworks, including base stations, that manage radio uplink, channelscalled uplink base stations SNBu and radio downlinks, called downlinkbase stations SNBd. It is allowed moreover that these base stations canexist in different numbers (at least in some coverage zones) and that,consequently, the two separate coverages, uplink and downlink, can begenerated with different numbers of cells.

The inventive concept consists then in a telecommunications networkcomprising three types of base stations:

-   -   1) a bidirectional base station SNB as shown in the FIG. 1        (called Node-B in UMTS terminology);    -   2) a downlink base station SNBd that manages only the        transmission channels using FDD technology in the downlink        direction. The station SNBd comprises a device which performs a        subset of functions carried out by the bidirectional base        stations SNB, and so can physically coincide with the base        stations SNB, as shown in the FIG. 2, but with the exception        that in some cases said base station SNB can be utilized without        managing the uplink transmission channels with FDD technology        and used instead for cellular coverage. In this last case, the        base station SNB will completely run the bi-directional        connections using Time Division Duplex (TDD) technology and all        the downlink channels (both those used for broadcast/multicast        and those for bidirectional connections);    -   3) an uplink base station SNBu that runs only uplink        transmitting channels using the FDD technology: this uplink base        station SNBu is made up of a low emission (negligible) device.        Since it performs a subset of functions performed by the normal        bi-directional base stations SNB, it can physically coincide        with the bidirectional base stations SNB, but can obtained in a        much simpler and more costless way since the base stations SNBu        , being specialized in managing uplink transmission channels        using FDD technology can perform only the minimum necessary        functions.

The utilization of low cost uplink base stations SNBu in greater numberthan the downlink base stations SNBd (that would also run the TDDconnections) allows to have a greater number of uplink channels, if theradio channels are utilized according to the form indicated in thedocuments that describe allocation of the spectrum for the 3G mobiletelecommunications systems. Such availability allows the utilization ofat least one (or more than one) less physical channel in the uplinksection and all without reducing the number of bidirectional symmetricalconnections permitted by the system.

The channels (or the frequency bands) thus spared can be usedadvantageously in other ways: for example, to support TDD connections orto house broadcast/multicast channels.

FIG. 2 shows a diagram of an access subsystem STA diagram composed ofradio base stations according to the invention. In this figure twodownlink base stations are shown, indicated respectively with SNBd(1)and SNBd(2), that communicate both in FDD modem indicated through arrowsF, and in TDD mode, indicated through arrows T, to which arerespectively associated three uplink base stations SNBu(_(1,1)),SNBu(_(1,2)), SNBu(_(1,3)), SNBU(_(2,1)), SNBU(_(2,2)), SNBU(_(2,3)).

The access subsystem STA of the telecommunications network according tothe invention originates a cellular coverage on the territory that isseparated for uplink and the downlink transmission, in a differentmanner from what is provided in the known cellular networkarchitectures.

Said access subsystem STA of FIG. 2 comprises thus, in additions tocanonical base stations SNB apt to run bidirectional communications whitthe user subsystem STU, also base stations SNBu suitable for supportingmonodirectional uplink transmission and also base stations SNBd suitablefor supporting monodirectional downlink transmission. In FIG. 2 onlybase stations SNBd are shown and not bidirectional base station SNB,since, as already mentioned, they can physically coincide.

Such access subsystem STA of FIG. 2 is included in thetelecommunications network according to the invention in an analogousway to that shown in FIG. 1, i.e. constitutes the access network forUMTS standard, the previously mentioned UTRAN and connects to atransport subsystem STT through a transport-access interface Iu.

From the above description the features of the present invention as wellas the relevant advantages thereof are clear.

In particular, are interesting the advantages of the base stations SNBu(mainly receiving), specialized in supporting uplink transmission.

In this regard it is observed that one of the most valuable resourcesfor a mobile telecommunication services provider is, in addition to thelicensed frequencies, the availability of the sites on which basestations SNB are installed; difficulties in finding sites are dueessentially to their transmission function and to the fact that suchstations generate an electromagnetical field, so that a specialauthorizations are required for installation.

Beyond the advantage already addressed, i.e., augmenting the capacity ofthe access subsystem as a whole with equal occupied frequencies andsites with transmission systems (that generate significantelectromagnetic fields), the invention offers other advantages whenapplied.

One further advantage of the invention is that it makes power controlless critical since, the uplink coverage cells being smaller, results tobe reduced the variability of the distance of the users system from thebase station uplink, and by consequence also the dynamics of the powercontrol: whereas the eventual imprecision of power control will be onaverage of minor amplitude.

Another advantage is determined by the fact that the distance from thereceiving base stations will always be less than that required in thecase with only base stations according to the prior art, therefore, theuser system will transmit with less power. This constitutes a doubleadvantage: less energy consumption, making the batteries last longer,and less user exposure to electromagnetic radiation having lowerintensity.

In addition, the telecommunications network for mobile users accordingto the invention is compatible with the UMTS and CDMA2000 standards andwith future systems based on analogous architecture that makes use ofopen interfaces with improvements in preceding systems.

It is obvious that many changes are possible to the telecommunicationsnetworks for mobile phone users, base stations, radio networkcontrollers and methods for transmitting data according to the presentinvention, without departing from the novelty spirit of the inventiveidea.

It is also clear that in practical development of the invention, theforms we have illustrated are only examples and can be substituted withequivalent technical elements.

The base station, according to the invention, allows distinct cellularcoverage for the downlink and uplink sections. FIG. 2 describes the onlycase in which there are more receiving cells or that the uplink coverageis denser, since this, the user communication to the network, is theportion currently more interesting, and that can be offered in the nearfuture offering major economic advantages derived from the UMTS servicesto customers. Finally, it is clear that the telecommunications networkaccording to the invention is not limited only to architecture foreseenby the UMTS standard. For example, it can be applied as well to the 2.5Gstandard.

The telecommunications network according to the invention can also beapplied to integration with wireless Local Area Networks (LAN). Thesignals based on these protocols can be carried out by means of anaccess subsystem through picocells with limited mobility such as thosefound at supermarkets and airports, using UMTS (or GSM-GPRS or WCDMA orUMT-2000 or further actual or future cellular systems in evolution)telecommunications networks which, through the use of the invention, canoffer special coverage for uplinks and downlinks.

1. A telecommunications network for mobile phone users comprising a usersubsystem and a transport subsystem associated by means of an accesssubsystem, which connect to them respectively through a user-accesscommunication interface and a transport-access communication interfacesuitable to allow the exchange of data flows between said subsystems,said access subsystem identifying a coverage area of thetelecommunication network for mobile users and comprising bidirectionalradio base stations and monodirectional radio base stations wherein atleast a part of the uplink communications between said user subsystemand said access subsystem are implemented by means of monodirectionalradio base stations dedicated only to uplink coverage, saidmonodirectional radio base stations dedicated only to uplink coverageusing a technique of transmissions separated in frequency forcommunicating with said user subsystem, said monodirectional radio basestations dedicated only to uplink coverage being located in the coveragearea of the mobile telecommunications network.
 2. A telecommunicationsnetwork for mobile phone users according to claim 1 wherein at least apart of the downlink communications, that is communications from theradio base station to the mobile phone user, are implemented by means ofmonodirectional radio base stations dedicated only to downlink coverage,said monodirectional radio base stations dedicated only to downlinkcoverage using a technique of transmission separated in frequency, saidmonodirectional radio base stations dedicated only to downlink coveragehaving means to communicate with radio network controllers.
 3. Atelecommunications network for mobile phone users according to claim 1wherein said monodirectional radio base stations dedicated only touplink coverage comprise means to communicate with radio networkcontrollers in the FDD technique.
 4. A telecommunications network formobile phone users according to claim 1 wherein said access subsystemcomprises radio network controllers that comprise means to communicatewith said monodirectional and bidirectional radio base stations.
 5. Atelecommunications network for mobile phone users according to claim 1wherein said monodirectional and bidirectional radio base stationscomprise means to communicate with the user subsystems, and that theuser subsystems comprise means to communicate with said monodirectionaland bidirectional radio base stations.
 6. A telecommunication networkfor mobile phone users according to claim 1 wherein said monodirectionalradio base stations dedicated only to uplink coverage comprise means forproviding one or more control channels, said control channels being ofbi-directional or monodirectional type.
 7. A telecommunications networkfor mobile phone users according to claim 1 wherein said monodirectionalradio base stations dedicated only to downlink coverage comprise meansfor providing one or more control channels, said control channels beingof bi-directional or monodirectional type.
 8. A telecommunicationsnetwork for mobile phone users according to claim 1 wherein the networkis based on the UMTS standard and access subsystem is based on the UTRANstandard.
 9. A telecommunications network for mobile phone usersaccording to claim 1 wherein the network is based on the 3G standardsthat make up the IMT2000 family.
 10. Method for developing cellularcoverage for a telecommunications network for mobile phone users using aFDD technique comprising the steps of implementing the radio coverage bymeans of bidirectional and monodirectional radio base stations, whereinat least a part of the uplink communications, that is communicationsfrom the mobile phone user to the radio base station, are implemented bymeans of monodirectional radio base stations dedicated only to uplinkcoverage, said monodirectional radio base stations dedicated only touplink coverage using a technique of transmission separated in frequencyfor said uplink communications, said radio base stations dedicated onlyto uplink coverage being located in the coverage area of the mobiletelecommunications network.